The Failure of Thin-Walled Semi-Elliptical Cylinders Under Torsion

Citation

Fredrick, Joseph Louis (1940) The Failure of Thin-Walled Semi-Elliptical Cylinders Under Torsion. Master's thesis, California Institute of Technology. doi:10.7907/31X1-Q070. https://resolver.caltech.edu/CaltechETD:etd-11132008-142412

Abstract

This paper constitutes a report on one phase of an investigation sponsored by the National Advisory Committee for Aeronautics at the California Institute of Technology, namely, the determination of the allowable loads in wing nose-sections under the action of combined loading conditions. As intimated by the title, the material presented here has been limited to the case of pure torsion only, this choice being dictated by the present state of the experimental program and the interpretation of its results. The experimental program itself consisted of the testing of specimens made up of two semi-elliptical (or semi-circular) segments of sheet supported and clamped at the ends of the minor axis of the ellipse, thus simulating two wing nose-sections mounted to a common spar and tested as a single unit. As a result of the testing of these specimens with varying ellipticity, sheet thickness, and length, sufficient experimental data was obtained to establish rational design curves for both the buckling and ultimate failure of semi-elliptical cylinders under torsion. Since the type of specimens used only approximated the shape of an actual wing nose-section, it was necessary to devise a means of relating the two structures, in order that the criteria presented in this paper could be used for actual design practice. Since a limited amount of torsion tests on actual wing assemblies was available to this author, it was used to check the validity of both the geometric relation devised between the two types of structures as mentioned above and the actual design criteria developed from the experimental results. The agreement obtained was quite good, thus substantiating the usefulness and reliability of the results presented in this paper. In the light of the above results, it is believed that the experimental portion of the investigation has been satisfactorily completed, with the possible exception of determining the affect of stiffeners upon the strength of the cylinders under discussion. However, since this represents an entirely different field of study, it is beyond the scope of this present investigation and must be relegated to the future. Attempts were made to develop a theoretical verification of the results obtained, but due to the complexities of the problem, they met with little success for the present. Therefore, this task also remains as one to be completed as a part of any future work which may be undertaken.

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